Find files which are created a certain time after or before a particular file was created

Try the following shell code:

file=</PATH/TO/FILE>
date=$(perl -le '$s = (stat($ARGV[0]))[9]; print $s;' "$file")
now=$(date +%s)
seconds=$((now - date))
mins=$((seconds / 60))
find . -mmin -$((mins + 60 )) -mmin +$((mins - 60)) -print

Another complicated option:

1. get test.txt's modification time (mtime)
2. calculate "before delta" = now + hour - mtime (assuming mtime is in the past)
3. calculate "after delta" = now - hour - mtime if now - mtime > hour else 0
4. run find -type f -mmin -"before delta" -mmin +"after delta"

It finds all files that are modified less than "before delta" minutes ago and greater than "after delta" minutes ago i.e., +/- hour around test.txt's modification time.

It might be simpler to understand if you draw now, mtime, "before", "after" times on a line.

date command allows to get now and mtime.

As a one-liner:

$ find -type f -newermt "$(date -r $file) -1 hour" -a \
            \! -newermt "$(date -r $file) +1 hour"